Critics of the emergency stockpile say the U.S. shale boom has made it unnecessary; supporters say it will be needed in a crisis

President Donald Trump’s proposal to help reduce the national debt by selling down more of the U.S. emergency oil stockpile is reigniting a debate about whether the reserves are still crucial to the country’s economic security.

The Trump administration said Tuesday that its new budget proposal calls for selling an additional 270 million barrels of oil over the next decade. Congress had already recently approved selling down some...